I think that you are making a false assumption by implying that DF owners purchased the camera exclusively to admire the buttons and not take pictures. I may be misunderstanding your point, I am not sure. I also think that many who are buying the camera use it as a professional tool on assignments even if it doesn't have dual card slots. I am not a professional photographer but have been using cameras for over 35 years. If I was being paid for an assignment , I would definitely be carrying two bodies instead of just one. A memory card can become corrupted but a camera body can also fail during a shooting session. Chances of a body failing are probably just as great as a memory card failing. Now I know that is not a solution for backing up your primary card, but at least you would be taking pictures with two bodies instead of just one.

Agree must have back up for important assignments - either back up cameras or better still back up photographers that you can trust.